The present invention relates to a toroidal-type continuously variable transmission to be used as, for example, an automotive transmission.
A related toroidal-type continuously variable transmission to be used as, for example, an automotive transmission is configured as illustrated in FIGS. 11 and 12. That is, an input disk 2 and an output disk 3 are rotatably supported on an input shaft 1, which is connected to a drive source (not shown) such as an engine, through a needle roller bearing. A cam plate 4 is spline-engaged with the input shaft 1 on the back-surface side of the input disk 2. A roller 5 is interposed between the cam plate 4 and the input disk 2. A loading cam or hydraulic loading pressing mechanism 6 for pressing the input disk 2 against an output disk 3 is provided therebetween.
Trunnions 8a and 8b each swinging about a pivot shaft 7 are provided between the input disk 2 and the output disk 3. A displacement shaft 9 is provided in each of the trunnions 8a and 8b through a radial needle roller bearing 8. A power roller 10 is rotatably supported on each of the displacement shafts 9 through an associated needle roller bearing 9a. Each of these power rollers 10 has a traction portion contacting the input disk 2 and the output disk 3 and is rolling-contacted therebetween in such a way as to tiltably rotate.
A power roller bearing 11 is provided between the power roller 10 and each of the trunnions 8a and 8b. This power roller bearing 11 allows the power roller 10 to rotate, while supporting a thrust load applied to the power roller 10. A plurality of balls 12 of such a power roller bearing 11 are held by an annular retainer 14 provided between an annular outer ring 13, which is provided at the side of each of the trunnions 8a and 8b, and the power roller 10 serving as a rotary portion. A radial bearing 16 is provided on a yoke 15 for tiltingly rotatably supporting each of the trunnions 8a and 8b, which supports the pivot shaft 7.
A valve body is placed under the input disk and the output disk. A mechanism for controlling a height position of the power roller is built into this valve body. This mechanism comprises an actuator, a hydraulic control valve for driving this actuator, and so on.
In the toroidal-type continuously variable transmission, power is transmitted between the power roller and each of the input disk and the output disk by interposing an oil film therebetween and using a shearing force of this oil film so as to secure traction. There are known techniques of thus providing a lubricating system in a toroidal-type continuously variable transmission, in which lubricating oil collected and stored in an oil pan is sucked up by an engine-driven oil pump having a line filter provided at the suction side thereof, and in which the lubricating oil is then supplied to the traction surfaces of an input disk and an output disk, and also a traction surface of a power roller through oil passages provided in drive rods of trunnions, (see, for example, the U.S. Pat. No. 6,238,318 and JP-A-2002-286110).
As described above, foreign substances, whose sizes are equal to or more than a predetermined size, can be eliminated by providing the line filter at the suction side of the oil pump. However, in a case where foreign substances unremoved by the line filter or burrs remain in the oil passage from the line filter to an oil passage outlet, or where dust enters there during fabrication of the transmission, foreign substances blow off to the power roller together with the lubricating oil.
The power roller bearing of the toroidal-type continuously variable transmission is used especially under a high bearing pressure at a high revolution rate. Thus, the related toroidal-type continuously variable transmission has a drawback in that such biting-in of foreign substances decreases the life of the power roller bearing.